1. Field of the Invention
The invention relates to truers, truing apparatuses including truers, grinders, and truing methods.
2. Description of the Related Art
A truing apparatus known in the related art is configured to shape the grinding surface of a grinding wheel using a truer in order to machine a workpiece into a desired shape or maintain the machining efficiency of a grinding process. A truer (which may also be referred to as a “dresser”) known in the related art and used for such a truing apparatus includes abrasive grains deposited on a core made of a metal material, such as iron or aluminum, by electrodeposition, for example. The abrasive grains on the truer are brought into contact with the grinding surface of a grinding wheel so as to slightly shave away the grinding surface, resulting in a new grinding surface having a desired shape.
Japanese Patent Application Publication No. 2015-77650 (JP 2015-77650 A) discloses a grinder including two disc-shaped truers protruding radially outward. The rotation axes of the two truers are perpendicular to each other. One of the truers effects truing on the outer peripheral surface of a grinding wheel, and the other truer effects truing on the end faces of the grinding wheel.
FIG. 7 of Japanese Patent Application Publication No. 8-192359 (JP 8-192359 A) illustrates a truer including diamond abrasive grains deposited on the outer peripheral surface of a truncated conical core that includes an edge. Using the diamond abrasive grains on the edge of the core of the truer, the outer peripheral surface and end faces of a grinding wheel are subjected to truing. First, the end face of the extremity of the truer is brought into contact with the outer peripheral cylindrical surface of the grinding wheel, and the truer is moved in parallel with the central line of the grinding wheel, thus effecting truing on the outer peripheral cylindrical surface of the grinding wheel using the abrasive grains on the edge. Subsequently, the truer is moved along the arc-shaped corner and the end face of the grinding wheel, thus effecting truing on the arc-shaped corner and the end face of the grinding wheel using the abrasive grains on the edge.
The grinder disclosed in JP 2015-77650 A requires the two truers. The number of truers is desirably one in order to reduce the size of the grinder. The truer disclosed in JP 8-192359 A enables truing on the outer peripheral surface and end faces of the grinding wheel by the single truer.
Unfortunately, effecting truing on the outer peripheral cylindrical surface of the grinding wheel using the truer disclosed in JP 8-192359 A brings a wide range of the end surface of the core into contact with the outer peripheral cylindrical surface of the grinding wheel. This significantly increases resistance during truing on the outer peripheral cylindrical surface of the grinding wheel. The increase in the resistance may move the truer itself away from the grinding wheel, causing the abrasive grains to shift from desired positions on the outer peripheral cylindrical surface of the grinding wheel. In such a case, the outer peripheral cylindrical surface of the grinding wheel may not be formed into a desired shape.
In effecting truing on the outer peripheral cylindrical surface of the grinding wheel, a truing method disclosed in JP 8-192359 A involves bringing the core into contact with the outer peripheral cylindrical surface of the grinding wheel before the abrasive grains come into contact with the outer peripheral cylindrical surface of the grinding wheel. This means that a force is exerted on the abrasive grains in a radially outward direction of the truer. Such a force may cause the abrasive grains to be separated from the core. If the abrasive grains are separated from the core in the course of truing on the outer peripheral cylindrical surface of the grinding wheel, the outer peripheral cylindrical surface will not be formed into a desired shape.